%% Copyright (c) 2011, INRA
%% 2005-2011, David Legland <david.legland@grignon.inra.fr>
%% 2011 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
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%% -*- texinfo -*-
%% @deftypefn {Function File} {varargout =} angleSort (@var{pts}, varargin)
%% Sort points in the plane according to their angle to origin
%%
%%
%%   PTS2 = angleSort(PTS);
%%   Computes angle of points with origin, and sort points with increasing
%%   angles in Counter-Clockwise direction.
%%
%%   PTS2 = angleSort(PTS, PTS0);
%%   Computes angles between each point of PTS and PT0, which can be
%%   different from origin.
%%
%%   PTS2 = angleSort(..., THETA0);
%%   Specifies the starting angle for sorting.
%%
%%   [PTS2, I] = angleSort(...);
%%   Also returns in I the indices of PTS, such that PTS2 = PTS(I, :);
%% 
%% @seealso{points2d, angles2d, angle2points, normalizeAngle}
%% @end deftypefn

function varargout = angleSort(pts, varargin)

  % default values
  pt0 = [0 0];
  theta0 = 0;

  if length(varargin)==1
      var = varargin{1};
      if size(var, 2)==1
          % specify angle
          theta0 = var;
      else
          pt0 = var;
      end
  elseif length(varargin)==2
      pt0 = varargin{1};
      theta0 = varargin{2};
  end


  n = size(pts, 1);
  pts2 = pts - repmat(pt0, [n 1]);
  angle = lineAngle([zeros(n, 2) pts2]);
  angle = mod(angle - theta0 + 2*pi, 2*pi);

  [dummy, I] = sort(angle);

  % format output
  if nargout<2
      varargout{1} = pts(I, :);
  elseif nargout==2
      varargout{1} = pts(I, :);
      varargout{2} = I;
  end

endfunction

%!shared p1,p2,p3,p4,pts,center
%! p1 = [0 0];
%! p2 = [10 0];
%! p3 = [10 10];
%! p4 = [0 10];
%! pts = [p1;p2;p3;p4];
%! center = [5 5];

%!test
%! expected = pts([3 4 1 2], :);
%! assert (expected, angleSort (pts, center), 1e-6);

%!assert (pts, angleSort (pts, center, -pi), 1e-6);